Authors

Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

2010

Journal

Diseases Of Aquatic Organisms

Volume

91

Issue

1

First Page

57

Last Page

66

Abstract

Crayfish populations in the area of the North Temperate Lakes Long Term Ecological Research (LTER) project, Wisconsin, USA, have been monitored for >25 yr. In 2005, native crayfish Orconectes propinquus from Big Muskellunge Lake were found with ulcerated lesions in the cuticle In 2006, lesions occurred in 9 5% of sampled crayfish from the lake (n = 3146). Ulcers generally occurred on the appendages of affected individuals but varied in location and severity. The prevalence of ulcers varied widely among sites, sample depths, and sampling dates, ranging from 20% The prevalence of ulcers in crayfish increased from a minimum in early June to a maximum in late July and August. In aquarium trials, healthy crayfish representing either O. propinquus or O. rusticus co-housed with ulcerated crayfish did not develop ulcers within 4 wk of exposure. Gross and histopathologic analyses of ulcerated crayfish revealed the presence of filamentous hyphae in the lesions while hemocytic infiltrates, melanotic reactions and silver-stained sections indicated that the ulcers had an oomycete etiology Excised samples of ulcerated crayfish cuticle grown in culture developed an oomycete that was identified as Saprolegnia australis by PCR amplification and sequence analysis of 2 different DNA fragments This is the first report of the occurrence of ulcers in wild crayfish associated with S. australis infection in the USA The advent of the outbreak and its underlying ecological causes are still under investigation.